1. Field of the Invention
This invention relates generally to drive devices and more particularly to drive devices wherein a flexible chain is utilized in tight engagement with a toothed wheel and drivingly engages a second toothed wheel for transmission of power axially.
2. Description of the Prior Art
There have been many prior art devices provided for the transmission of power, such as conventional meshing gears which have long been utilized for the transmission of power and to achieve increase or decrease in speed. Also, flexible roller type chains have been utilized in many applications for power transmission, the chains being normally interconnected between two different sprocket wheels, thereby transmitting the power between them in a longitudinal direction along the chain, their axes being generally parallel.
There have also been prior devices adapted to provide gearing, or so-called gearing wherein a chain is wrapped around a large toothed wheel and drivingly engages a smaller toothed wheel which is axially spaced from the longer wheel for essentially the transmission of power in an axial direction.
One such prior art proposal has provided a chain having the same number of links as teeth in the larger wheel and wherein the chain is loosely or floatingly engaged on teeth of the large toothed wheel and drivingly engages a smaller toothed wheel.
However, this type of securing of the chain to the larger toothed wheel has resulted in failure of the chain under loads. Devices constructed with this floating chain arrangement find certain advantageous usages, especially under conditions of light loading, and provide an economical solution to certain power transmission applications. However, under heavier loading conditions this floating chain arrangement has exhibited certain serious disadvantages and has not proved entirely satisfactory, this arrangment having a tendency to fail under heavier loads after a relatively short operating life.
After analyzing various failures, it was determined that the loads imposed on the floating chain resulted in a skewing and tilting of the chain. This, in turn, caused a serpentine movement of the chain as the unit revolved. The serpentine motion, together with its causation factors, in turn provides excessive localized stress patterns, thereby resulting in uneven and excessive wear of the teeth of the wheel and pins of the chain, thus causing early failure. Also, with this floating chain arrangement there may be sufficient distortion of the chain to cause it to "jump" the teeth of the wheel.